1. Field of the Invention
The present invention relates generally to a throttle control mechanism and, more particularly, to a structure by which a rotational position sensor and a throttle control mechanism are directly mounted, for support, to a throttle body for purposes of vibration isolation and associated with each other in a force transmitting relationship which utilizes a cam structure.
2. Description of the Prior Art
Many different systems are well known to those skilled in the art for the purpose of controlling the movement of a throttle plate within a throttle body structure and monitoring the angular position of the throttle plate relative to the throttle body structure. Some systems of this type mount a rotational position sensor directly to the throttle body for the purpose of having the movable portion of the rotational position sensor rotate about the axis of rotation of the throttle plate. Other known systems mount a rotational position sensor at a region of an internal combustion engine away from the throttle body structure and connect the throttle plate axis to the rotational position sensor with a linkage arrangement so that the two components rotate about their respective axes in a coordinated manner.
U.S. Pat. No. 6,341,593, which issued to Kamimura et al on Jan. 29, 2002, describes a throttle apparatus for an engine. An electronic throttle apparatus permits aggregating of various parts and rationalization of installation, and can simplify assembling operation and wiring operation to an engine room for rationalization of an installation space. The throttle apparatus for an engine includes a throttle body housing therein a throttle valve and disposed in an air intake of the engine, a throttle actuating motor, a throttle position sensor detecting a throttle valve angle and an air flow sensor located upstream of the throttle valve and measuring an intake air flow rate. The throttle actuating motor, the throttle position sensor, and the air flow sensor are mounted on the throttle body.
U.S. Pat. No. 6,228,534, which issued to Starkweather et al on Sep. 11, 2001, describes a non-contacting throttle valve position sensor. The throttle valve position sensor has a non-contacting, magnetic field sensor coupled to or integral with a gear wheel of a geared throttle valve control. The sensor provides a more durable sensor. Sensor circuitry can be provided on the lid of the control, along with control motor electrical connections, so that the sensor and control motor can be connected by simple joining in a single operation. The throttle control valve is intended for internal combustion engines for motor vehicles.
U.S. Pat. No. 6,029,510, which issued to Nakaie et al on Feb. 29, 2000, describes a rotary throttle position sensor. The device is related to a rotary throttle position sensor for detecting the position of a throttle shaft of an internal combustion engine, and aims to increase the reliability in installation on a throttle shaft. The rotor prior to installation is provisionally retained in position to always ensure the initial point of rotation by making a protrusion provided on the rotor touch and ride over a protrusion provided on the cover, thereby the rotor is pressed to the case when the cover is assembled on the case.
U.S. Pat. No. 6,019,083, which issued to Isogawa on Feb. 1, 2000, describes a throttle and sensor arrangement for an engine. A throttle control system for an outboard motor and throttle position sensor therefore that permits a compact assembly by operating the throttle valve via an intermediate throttle valve operating shaft that is disposed closer to the body of the engine and farther from the protective cowling than the throttle valve. A throttle position sensor is associated with this intermediate throttle operating shaft for providing a signal indicative of throttle valve position for engine control.
U.S. Pat. No. 5,967,861, which issued to Ozawa et al on Oct. 19, 1999, describes a throttle position sensor mounting arrangement for a personal watercraft engine. The mounting arrangement for a throttle position sensor associated with a throttle valve is described. The throttle valve is positioned within an intake pipe of an intake system of an engine which is positioned in an engine compartment defined by a hull of a watercraft. An output shaft of the engine is arranged to drive a water propulsion device of the watercraft. The intake pipe extends from the engine and is arranged to route air to a combustion chamber of the engine. The throttle position sensor is mounted so as to be shielded by the intake pipe from a source of water within the engine compartment, such as an outlet of an intake duct leading through the hull of the watercraft.
U.S. Pat. 5,756,890, which issued to Fedison, Jr. on May 26, 1998, describes a snap mount throttle position sensor. A throttle body assembly is provided for use in the air intake system of an internal combustion engine. The throttle body assembly includes a plastic throttle body housing and a throttle position sensor mounted thereto. The housing and throttle position sensor each have a mounting flange with one flange telescopically insertable into a pocket in the other flange. A snap fit mechanism will securely hold the two mounting flanges together in the proper orientation.
U.S. Pat. No. 5,704,334, which issued to Kato on Jan. 6, 1998, describes an engine throttle sensor. The throttle sensor senses the position of an associated throttle shaft in order to determine the position of a corresponding throttle valve. The position of the throttle sensor is positioned in the engine to reduce the girth of the engine. In one embodiment, the throttle sensor lies to the side of a throttle linkage which interconnects a plurality of throttle valves. The throttle sensor and throttle linkage are arranged on a side of an intake manifold opposite a side on which fuel injectors of the engine are located. In another embodiment, the throttle sensor lies at an upper end of the intake manifold and is coupled to a common, vertically oriented throttle shaft that operates a plurality of throttle valves.
U.S. Pat. No. 5,273,016, which issued to Gillespie et al on Dec. 28, 1993, describes a throttle lever position sensor for a two stroke fuel injected engine. A marine propulsion device comprises a propulsion unit which is adapted to be mounted on a boat and which includes a propeller shaft and an internal combustion engine drivingly connected to the propeller shaft. The engine includes an engine block structure having a combustion chamber and defining an air intake passage communicable with the combustion chamber. A throttle plate is moveably supported by the engine block structure and located in the air intake passage, with the structure for moving the throttle plate in response to movement of an operator control member. The structure is supported by the engine block structure for providing a signal indicating the position of a control member independent of the position of the throttle plate.
U.S. Pat. No. 4,864,996, which issued to Hensel on Sep. 12, 1989, discloses a fuel injected two cycle engine with progressive throttle linkage for improved resolution of a throttle position sensor. A two cycle crankcase compression fuel injected internal combustion engine has a first set of one or more throttle valves controlling combustion air flowing into the crankcase and a second set of one or more throttle valves also controlling combustion air flowing into the crankcase. A throttle position sensor controls fuel injection according to throttle position. Increased resolution of sensed throttle position at low engine speed is provided by admitting combustion air only through the first set of throttle valves and not through the second set of throttle valves at low engine speed for an initial given range of motion, such that greater movement of the first set of throttle valves is required to obtain a given amount of combustion air flow for a given engine speed, prior to opening the second set of throttle valves, to provide more accurate fuel injection and better driveability. Progressive throttle linkage is movable to open the first set of throttle valves through a given range of motion prior to opening the second set of throttle valves.
The patents described above are hereby expressly incorporated by reference in in the description of the present invention.
Numerous conditions affect the operability of a throttle control mechanism which comprises a rotational position sensor. For the purpose of accuracy and avoiding deterioration, it is beneficial if the rotational position sensor is mounted in such a way that it is protected from severe vibrations that could be caused by the engine""s operation. The method of connecting a rotational position sensor to a throttle valve can introduce excessive lost motion which, in itself, can introduce additional error in the signal provided by the rotational position sensor which is intended to be representative of the throttle plate position. The method and location of mounting a rotational position sensor with respect to a throttle plate also necessitates certain spatial requirements, particularly in restricted volumes such as those typically available in conjunction with engines used in outboard motors. Furthermore, the relationship between a rotational position sensor signal and the actual throttle plate position can benefit from more accuracy and resolution during certain portions of the throttle plate""s rotation than during other portions of the throttle plate""s rotation. More resolution allows an engine control unit (ECU) to more precisely control the position of the throttle plate during certain ranges of the operation of the engine.
It would therefore be significantly beneficial if a throttle control system could mount a rotational position sensor directly to a throttle body in such a way that it is not mounted directly for rotation about the axis of the throttle plate itself. It would also be beneficial if the throttle position sensor could be mounted to the throttle body structure in such a way as to take advantage of the vibration isolation components associated with the throttle body structure. In addition, is would significantly beneficial if the relationship between the rotation of the rotational position sensor and the rotation of the throttle plate could be calibrated so that they are not necessarily associated in a linear relationship with each other.
A throttle control mechanism, made in accordance with a preferred embodiment of the present invention, comprises a throttle body structure and a throttle plate that is rotatable about a throttle axis relative to the throttle body structure. It also comprises a rotational position sensor comprising a stationary portion and a movable portion which is rotatable about a sensor axis. The throttle plate and the movable portion of the rotational position sensor are associated in force transmitting association with each other, wherein rotation of the movable portion of the rotational position sensor about the sensor axis causes the throttle plate to rotate about the throttle axis. The sensor axis is displaced from the throttle axis.
A preferred embodiment of the present invention further comprises a cam member attached to the movable portion of the rotational position sensor. The cam member has a cam surface. It also comprises a cam follower attached to the throttle plate. The cam follower is disposed in contact with the cam surface. The cam surface is shaped to cause the throttle plate to rotate about the throttle axis in a non linear relationship to the movable portion of the rotational position sensor which rotates about the sensor axis. A throttle cable is connected in force transmitting association with the movable portion of the rotational position sensor to cause rotation of the movable portion of the rotational position sensor about the sensor axis in response to movement of the throttle cable. The stationary portion of the rotational position sensor is rigidly attached to the throttle body structure. The cam follower comprises a cam follower arm rotatably attached to the throttle body structure and a cam follower wheel which is rotatably attached to the cam follower arm for rotation about a wheel axis. The cam follower wheel is disposed be in rolling contact with the cam surface.